In order to deal with challenges of wireless broadband technology and ensure the leading position of the 3rd Generation Partnership Project (3GPP) network, the 3GPP has initiated the Long Term Evolution (LTE) program. Under the guidance of the LTE program, a new architecture for mobile communication networks is defined, which is flatter than the existing General Packet Radio Service/Universal Mobile Telecommunications System (GPRS/UMTS), and only keeps a Packet Switched (PS) domain, and thus is called Evolved Packet System (EPS). No matter for the current GPRS/UMTS system, the upgraded Release-8 GPRS/UMTS system, or the EPS network being researched, User Equipment (UE) shall be first registered into the network before establishing a Packet Data Protocol (PDP) context bearer or an EPS bearer, and acquire an Internet Protocol (IP) address in order to enforce PS service. The so-called PDP context bearer or EPS bearer is a logical tunnel for transmitting various service data streams. The UE connects to the specific application server in a Packet Data Network (PDN) for transmitting data packet via the bearer. Multiple bearers connected to the same PDN may be considered as one PDN connection. In a pre-Release-8 GPRS/UMTS system, the UE can only acquire one IP address per PDN connection; while in the Release-8 GPRS/UMTS or EPS, if the UE's capability and the network equipment's capability are allowed, the UE is able to acquire two IP addresses with different IP version, that is, an IP version 4 (IPv4) address and an IP version 6 (IPv6) address, per one PDN connection.
In the implementation of the present disclosure, the inventor finds that when the first bearer of one PDN connection is established, the UE may subsequently initiate a new process to acquire an IP address for the PDN connection, and the IP address may be an IP address with another version that has not been acquired by the UE, or a new IP address. As such IP address acquirement process requires that the UE and network equipment support certain related capabilities, it is possible that it will fail for the UE to apply for an IP address for one PDN connection when the network equipment does not allow the UE to acquire two IP addresses for the PDN connection, which results in resource waste, and even results in interruption of an ongoing service in the PDN connection.